Method and apparatus for optical detector with special discrimination

ABSTRACT

A monolithic optical detector for determining spectral content of an incident light includes at least a first and second well in a substrate, the second well formed proximate the first well. The first well is configured to be exposed to incident light and for generating a first photocurrent as a function of the incident light. The second well is configured to be shielded from the incident light and for generating a second photocurrent as a function of the incident light. Lastly, a processing and control unit, responsive to the first and second photocurrents, determines an indication of spectral content of the incident light. A method and device parameter controller are also disclosed.

BACKGROUND

The present invention relates generally to semiconductor devices, andmore particularly, to a method and apparatus for an optical detectorwith spectral discrimination using conventional CMOS components.

Detection of ambient light levels is necessary for purposes such asautomatic control of artificial light levels. Silicon photodiodes orphototransistors are frequently employed for this purpose, since theyare inexpensive and easy to use. In addition, the silicon photodiodes orphototransistors may be part of an integrated circuit.

However, the response of silicon photo detectors does not match that ofthe human eye. Depending on the light source and its power spectrum, thedifference in brightness as perceived by the human eye and a siliconphoto detector can vary greatly. As an example, fluorescent lighting hasa spectrum that falls largely within the range of the human eyeresponse, while incandescent lighting emits much of its energy in theinfrared (IR) region of the spectrum. A simple silicon photo detectorcan give a response as much as four (4) times greater for incandescentlighting than for fluorescent lighting for a brightness level which isperceived by the human eye to be the same.

Sunlight has a spectrum between those of fluorescent lighting andincandescent lighting. The ratio of infrared emission to visibleemission is highest for incandescent lighting, lowest for fluorescentlighting, and medium for sunlight.

Despite the above discussion, silicon photo detectors can be used formeasuring light levels as perceived by the human eye. This can beaccomplished by placing an optical filter between the light source andthe detector. In doing so, the optical filter enables the compositeresponse to mimic that of the human eye. While this is an effectivesolution, the filter implies additional expense.

SUMMARY

A monolithic optical detector for determining spectral content of anincident light includes at least a first and second well in a substrate,the second well formed proximate the first well. The first well isconfigured to be exposed to incident light and for generating a firstphotocurrent as a function of the incident light. The second well isconfigured to be shielded from the incident light and for generating asecond photocurrent as a function of the incident light. Lastly, aprocessing and control unit, responsive to the first and secondphotocurrents, determines an indication of spectral content of theincident light. A method and device parameter controller are alsodisclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an optical detector with spectraldiscrimination device according to one embodiment of the presentdisclosure;

FIG. 2 is a plan view of an optical detector with spectraldiscrimination according to another embodiment of the presentdisclosure;

FIG. 3 is a block diagram view of an optical detector with spectraldiscrimination system according to another embodiment of the presentdisclosure; and

FIG. 4 is a block diagram view of a display controller having an opticaldetector with spectral discrimination according to another embodiment ofthe present disclosure.

DETAILED DESCRIPTION

With reference to FIG. 1, an optical detector with spectraldiscrimination according to an embodiment of the present disclosure isreferred to, in general, by the reference numeral 10. The detector 10includes a first well 12 and a second well 14, proximate the first well,the first and second wells being disposed in substrate 16.

According to one embodiment, substrate 16 includes a p-type siliconsubstrate. First and second wells 12 and 14, respectively, includen-type wells. The first and second wells are of substantially similardimensions and formed in substrate 16 using standard CMOS integratedcircuit fabrication techniques, as known in the art.

First well 12 is configured to be exposed to incident light 18. Secondwell 14 is configured to be shielded from the incident light 18.Incident light 18 may include, for example, fluorescent light,incandescent light, or sunlight. At least one transparent layer 20 isdisposed above at least the first well 12. In addition, at least onelayer 22, opaque to incident light 18, is disposed above second well 14.Layer 20 includes any transparent layer, for example, an oxide layer.Layer 22 includes any layer opaque to incident light 18, for example, anopaque conductive layer.

Prior to further discussion of detector 10, let us consider thefollowing. When a photon of incident light is absorbed in silicon, ahole-electron pair is generated. A minority carrier diffuses through thesilicon lattice until it either recombines or encounters a diodejunction. When the minority carrier encounters a diode junction, it canbe collected as photocurrent. The minority carrier is also referred toas a photo carrier.

Photon absorption is a random process, wherein the likelihood of thephoton being absorbed in silicon is a function of wavelength. Anabsorption distance is herein defined as a distance that a quantity 1/eof the incident light travels before being absorbed, wherein erepresents the natural logarithm. For the visible wavelengths in therange of 400 to 700 nanometers, the absorption distance is on the orderof 3.4 microns or less. At 800 nanometers, the absorption distance is onthe order of about 8 microns. At 900 nanometers, the absorption distanceis on the order of about 22 microns. At 1000 nanometers, the absorptiondistance is on the order of about 93 microns.

According to one embodiment of the present disclosure, the opticaldetector with spectral discrimination method and apparatus makes use oftwo fundamental facts. The first is that diffusion of minority carriersin a silicon lattice is a random, three-dimensional process. The secondis that the absorption distance of light in silicon varies greatly as afunction of wavelength.

In standard CMOS integrated circuits, the deepest diode junction isgenerally a well/substrate junction. For example, the well/substratejunction may include an n-well/p-substrate junction. Such awell/substrate junction is typically on the order of about 4.0 micronsdeep for a 0.8 micron process. The well/substrate junction depth maydiffer from 4.0 microns deep for a CMOS process other than the 0.8micron process.

When such a well/substrate junction diode is used as a photodiode, suchas is commonly done in integrated CMOS optoelectronic circuits, mostphotons of visible wavelengths impinging on the diode are absorbedwithin the well. The remaining photons are absorbed below thewell/substrate junction. Almost all the photo carriers generated withinthe well or the depletion region surrounding the well junction arecollected as photocurrent. A small fraction will be lost torecombination.

The fate of carriers generated below the well/substrate junction of thephotodiode, however, depends on their distance from the junction. If thevertical distance below the well is small compared to the lateraldimensions of the diode and the carrier mean diffusion length, then itis highly probable that a photo carrier will be collected by the diodeas photocurrent. As the distance below the well increases, a photocarrier is more likely to experience significant lateral, as well asvertical, diffusion.

With sufficient lateral diffusion, a photo carrier can travel far enoughaway from the photodiode to be collected by any additional diodesadjacent to, or proximate the vicinity of, the photodiode. If otherdiodes adjacent to the photodiode are shielded from light, then anyphoto carriers that the shielded diodes collect will be due to photonsabsorbed below the photodiode junction. Accordingly, it follows that thedeeper a photon is absorbed, the more likely it is to be collected by anadjacent diode proximate the vicinity of the photodiode.

If a structure is designed that includes a photodiode exposed to lightin close proximity to one or more diodes shielded from light, then theratio of the photocurrents is indicative of the spectral content of thelight. More specifically, the higher the ratio of the dark diode currentto the illuminated diode, the greater the long wavelength content.

Returning again to FIG. 1, detector 10 includes an optical detector withspectral discrimination according to an embodiment of the presentdisclosure. In FIG. 1, diode D1 (12) includes an n-well/p-substratediode which is exposed to incident light (18). Diodes D2 (14) and D3(24) are similar diodes which are shielded from the incident light 18.Shielding implies that diodes D2 and D3 are not directly exposed to theincident light.

A carrier, e, indicated in general by reference numeral 26, is generatedby a photon being absorbed below the diode D1 junction. To a firstapproximation, the relative probability that the carrier will becollected by a given diode is proportional to the solid angle subtendedby the carrier and the respective diode.

For equally sized diodes, angle α1 will be greater than angle α2, whichis in turn greater than angle α3. Expressed another way, α1>α2 andα2>α3. For carriers generated immediately below diode D1 (i.e., incidentlight of shorter wavelengths) the ratio of α1 to α2 is quite large.However, as the depth of the carrier increases (i.e., incident light oflonger wavelengths), the ratio of α1 to α2 and ratio of α2 to α3asymptotically approach the value of one (1), as does the ratio of therespective photocurrents.

By measuring the ratio of the photocurrents of diode D1 (12) and diodeD2 (14), it is possible to infer wavelength information about amonochromatic light source. The ratio of photocurrents can also be usedto estimate the relative spectral content of a broad band light sourcein order to establish the type of light source. More specifically,according to one embodiment of the present disclosure, this method ofspectral discrimination can be used to categorize a light source asfluorescent, incandescent or sunlight.

Additional information regarding spectral content can be inferred fromthe ratio of diode D3 current to diode D2 and diode D1 currents.Furthermore, the concept of the present embodiments can in theory beextended to any number of diodes.

FIG. 1 further illustrates another embodiment of the present disclosure.Diodes D2B (28) and D3B (30) can be made parallel with diodes D2 (14)and D3 (24), respectively, to increase the collection efficiency of thedark diodes. The basic structure of diodes D1 (12), D2 (14), D3 (24),D2B (28) and D3B (30) of FIG. 1 can also be extended to include arepetitive array of light and dark structures, as shown in FIG. 2.

For example, the first well can include a plurality of first wells D1,wherein the plurality of first wells generate a plurality of first photocurrents as a function of the incident light. The second well caninclude a plurality of second wells D2, wherein the plurality of secondwells generate a plurality of second photo currents as a function of theincident light. An indication of spectral content of the incident lightis determined in response to the plurality of first photo currents andthe plurality of second photo currents.

Still further, the plurality of first wells may include an array offirst wells and the plurality of second wells further includes an arrayof second wells proximate respective ones of the array of first wells.The well structures could still further be constructed using concentricgeometries.

In alternate embodiments, the first and second wells may further includep-type wells in an n-type substrate, shallow diffusions, deepdiffusions, combinations of shallow and deep diffusions, andsource/drain diffusions. Still further, the first and second wells mayinclude charge gate MOS diode structures in which a potential applied tothe gates of the structures establishes the respective wells.

Turning now to FIG. 3, another embodiment of the present disclosureincludes an Ambient Light Detector (ALD), generally indicated byreference numeral 40. The ALD includes a multiplexer (MUX) 42, an analogto digital (A/D) converter 44, and processing and control unit(PROCESSING AND CONTROL) 46.

MUX 42 includes inputs IN1, IN2, and IN3 indicated by reference numerals48, 50 and 52, respectively. MUX 42 also includes an output 54. MUX 42is responsive to a selection signal on selection input 56 for couplingone of inputs IN1, IN2, and IN3 to output 54.

The output 54 of MUX 42 couples to input 58 of A/D converter 44. A/Dconverter 44 converts a signal received at input 58 into a digitalquantity at output 60, in response to a control signal at control input62.

The output 60 of A/D converter 44 couples to input 64 of PROCESSING ANDCONTROL 46. PROCESSING AND CONTROL 46 provides spectral information onoutput 66 in response to the digital input at 64. Output 66 providesspectral content information according to the requirements of aparticular ambient light detector application. In addition, PROCESSINGAND CONTROL 46 provides suitable control signals on control output 68 toselect input 56 of MUX 42 and control input 62 of A/D converter 44,further according to the requirements of a particular ambient lightdetector application.

In FIG. 3, diodes D1 (12), D2 (14) and D3 (24) include the light anddark diodes, as previously described with respect to FIG. 1. Diodes D1(12), D2 (14) and D3 (24) couple to inputs 48, 50, and 52, respectivelyof MUX 42. MUX 42 is responsive to a selection signal on a select inputfor selecting one of the three diodes for input to the A/D converter 44.A/D converter 44 converts a selected one of the output photocurrents ofthe photodiodes into a representative digital quantity.

In one embodiment, A/D converter 44 integrates a respective one of theinput photocurrents over a sufficient time period to average a ripple inthe incident light caused by alternating current (AC) lighting. Inanother embodiment, A/D converter 44 utilizes a logarithmic compressionfor extending a dynamic range of a photocurrent received at the input ofthe A/D converter.

In one embodiment, PROCESSING AND CONTROL 46 includes digital circuitryfor controlling the MUX 42 and A/D converter 44 according to a desiredambient light detector application. PROCESSING AND CONTROL 46 may alsocontain circuitry for further conditioning the output 60 of the A/Dconverter 44 and translating the results of the conditioned A/D outputinto spectral information. For example, conditioning may include timeaveraging, amplitude compression, or other conditioning suitable for aparticular ambient light detector application.

According to another embodiment, the PROCESSING AND CONTROL unit furthercontains programmable calibration circuitry, the calibration circuitryconfigured to account for carrier lifetime differences on differentchips. For example, the programmable calibration circuitry can enablecalibrating of at least the first and second photocurrents of diodes D1(12) and D2 (14). In addition, the ambient light detector ALD 40 mayinclude fuses (not shown) associated with the PROCESSING AND CONTROLunit 46 to accomplish the calibration, as may be required. For instance,the fuses could be trimmed during an integrated circuit probe step inthe manufacturing process.

According to yet another embodiment, PROCESSING AND CONTROL unit 46performs a translation of the conditioned A/D converter output thatincludes, for example, arithmetic processing and use of a table look-up.The translation may be also be accomplished with at least one ofhard-wired logic and stored program logic, such as via a microprocessor.

PROCESSING AND CONTROL 46 may also include means, coupled to the outputof A/D converter 44 and implemented on the monolithic integratedcircuit, for establishing a spectral content response configured tosimulate that which would be observed by a human eye.

Referring now to FIG. 4, a block diagram view of a display controllerhaving an optical detector with spectral discrimination according toanother embodiment of the present disclosure shall be discussed. Thedisplay controller is generally indicated by reference numeral 70.Display controller 70 includes ambient light detector 40 coupled to acontroller 72. Controller 72 couples to display 74. Controller 72 mayinclude any suitable control device, circuit, or processor forperforming the desired functionality, as discussed herein.

Ambient light detector 40 includes a monolithic optical detector asdiscussed above with respect to FIG. 3. Ambient light detector 40provides an indication of the spectral content of the incident light 18to controller 72. In one embodiment, controller 72 includes a backlightcontroller, responsive to the indication of spectral content of theincident light 18 for controlling a backlighting of display 74.

Display 74 may include any display responsive to a backlight controlsignal for producing a desired backlighting with an artificialillumination. An illustrative device may include a display for a laptopcomputer, for example. Controlling the backlighting of the displayscreen according to the spectral content of ambient incident light onthe laptop computer can facilitate improved power management, extendinga useful battery life between recharging periods of the same. Otherelectronic devices, such as hand held electronic devices, capable ofproviding backlighting with an artificial illumination, are alsocontemplated.

Alternatively, controller 72 may include a means for controlling adevice parameter in response to the indication of spectral content ofthe incident light. The device parameter may include any parameter of adevice controlled in response to the indication of spectral content ofthe incident light. The device parameter may include, for example, abacklight control parameter of a display device. The backlight controlparameter may include at least a first artificial illumination level fora first type of incident light and a second artificial illuminationlevel for a second type of incident light. The first and secondartificial illumination levels can include, for example, backlightingand no backlighting, respectively. The first and second artificialillumination levels may also include additional levels of differentartificial illumination.

The device parameter may also include, for example, a color controlparameter of a color display. The color control parameter is configuredto change the display color characteristics to adapt to environmentallight incident upon the display. In this example, controller 72 adjuststhe color content of the display in response to the indication ofspectral content of the ambient light detected by detector 40.

In another embodiment, controller 72 and PROCESSING AND CONTROL 46include the same device having functionality as desired for a givenoptical detection and control application.

Although only a few exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. For example, the functionality of thevarious embodiments as discussed herein can be provided on a singlemonolithic integrated circuit. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents, but alsoequivalent structures.

What is claimed is:
 1. A monolithic optical detector comprising: a firstwell in a substrate, said first well configured to be exposed toincident light and for generating a first photocurrent as a function ofthe incident light; a second well in the substrate, proximate said firstwell, said second well configured to be shielded from the incident lightand for generating a second photocurrent as a function of the incidentlight; and means, responsive to the first and second photocurrents, fordetermining an indication of spectral content of the incident light. 2.The detector of claim 1, wherein said means for determining theindication of spectral content includes determining a ratio of the firstand second photocurrents, wherein the ratio provides a measure ofspectral content.
 3. The detector of claim 2, wherein the ratio furtherincludes at least one of a first measurement range representative of afirst type of incident light, a second measurement range representativeof a second type of incident light, and a third measurement rangerepresentative of a third type of incident light.
 4. The detector ofclaim 3, wherein the first, second, and third type of incident lightinclude at least one of fluorescent light, incandescent light, and sunlight.
 5. The detector of claim 1, wherein said first and second wellsinclude at least one of n-type wells in a p-type substrate, p-type wellsin an n-type substrate, shallow diffusions, deep diffusions,combinations of shallow and deep diffusions, source/drain diffusions,and charge gate MOS diode structures.
 6. The detector of claim 1,further wherein said first and second wells include wells ofsubstantially similar dimensions.
 7. The detector of claim 1, whereinthe indication of spectral content includes a wavelength.
 8. Thedetector of claim 1, further comprising: means for calibrating at leastone of the first and second photocurrents.
 9. The detector of claim 1,further comprising: at least one transparent dielectric layer disposedabove at least said first well; and at least one opaque layer disposedabove said second well.
 10. The detector of claim 9, wherein the atleast one opaque layer includes a conductive layer.
 11. The detector ofclaim 1, further comprising: at least one additional well in thesubstrate, proximate said first and second wells, said at least oneadditional well configured to be shielded from the incident light andfor generating at least one additional photocurrent as a function of theincident light, respectively; and wherein said means for determining theindication of spectral content includes means, responsive further to theat least one additional photocurrent, for determining the indication ofspectral content of the incident light.
 12. The detector of claim 11,wherein said means for determining the indication of spectral contentincludes determining a ratio of the first and second photocurrents, theratio providing a measure of spectral content, further includingdetermining at least one additional ratio of the second and at least oneadditional photocurrents, wherein the at least one additional ratioprovides an additional measure of spectral content of the incidentlight.
 13. The detector of claim 12, wherein the ratio and at least oneadditional ratio further include at least one of a first measurementrange representative of a first type of incident light, a secondmeasurement range representative of a second type of incident light, anda third measurement range representative of a third type of incidentlight, respectively.
 14. The detector of claim 13, wherein the first,second, and third type of incident light include at least one offluorescent light, incandescent light, and sun light.
 15. The detectorof claim 11, further wherein said first, second, and at least oneadditional wells include wells of substantially similar dimensions. 16.The detector of claim 1, further comprising: at least oneanalog-to-digital (A/D) converter integrated with said first and secondwells and formed as a monolithic integrated circuit, said first andsecond wells being coupled to at least one input of said at least oneA/D converter for converting a respective one of the first and secondphotocurrent into a digital output.
 17. The detector of claim 16,wherein further comprising: a multiplexer coupled between said first andsecond wells and an input of said A/D converter, said multiplexer forselectively coupling the first and second photocurrents to the input ofsaid A/D converter.
 18. The detector of claim 16, wherein said at leastone A/D converter integrates a respective one of the first and secondphotocurrents over a sufficient time period to average a ripple in theincident light caused by alternating current (AC) lighting.
 19. Thedetector of claim 16, further comprising: means, coupled to an output ofsaid at least one A/D converter and implemented on the monolithicintegrated circuit, for establishing a spectral content responseconfigured to simulate that which would be observed by a human eye. 20.The detector of claim 16, wherein said at least one A/D converterutilizes a logarithmic compression for extending a dynamic range of aphotocurrent received at the at least one input of said at least one A/Dconverter.
 21. The detector of claim 1, further comprising: means,coupled to said determining means, for controlling a device parameter inresponse to the indication of spectral content of the incident light.22. The detector of claim 21, wherein the device parameter includes atleast one of a backlight control parameter of a display and a colorcontrol parameter of a color display.
 23. The detector of claim 22,wherein the backlight control parameter includes at least a firstartificial illumination level for a first type of incident light and asecond artificial illumination level for a second type of incidentlight.
 24. The detector of claim 1, wherein said first well includes aplurality of first wells, the plurality of first wells for generating aplurality of first photo currents as a function of the incident light,wherein said second well includes a plurality of second wells, theplurality of second wells for generating a plurality of second photocurrents as a function of the incident light, and wherein saiddetermining means determines an indication of spectral content of theincident light in response to the plurality of first photo currents andthe plurality of second photo currents.
 25. The detector of claim 24,wherein the plurality of first wells further includes an array of firstwells and the plurality of second wells further includes an array ofsecond wells proximate respective ones of the array of first wells. 26.The detector of claim 25, still further wherein the array of first wellsand the array of second wells include repetitive arrays.
 27. Thedetector of claim 25, wherein the arrays of first and second wells forma concentric geometry of first and second wells.
 28. A method fordetermining spectral content of incident light upon a monolithic opticaldetector comprising: generating a first photocurrent as a function ofthe incident light at a first well in a substrate, the first wellconfigured to be exposed to incident light; generating a secondphotocurrent as a function of the incident light at a second well in thesubstrate proximate the first well, the second well configured to beshielded from the incident light; and determining an indication ofspectral content of the incident light in response to the first andsecond photocurrents.
 29. The method of claim 28, wherein determiningthe indication of spectral content includes determining a ratio of thefirst and second photocurrents, wherein the ratio provides a measure ofspectral content.
 30. The method of claim 29, wherein the ratio furtherincludes at least one of a first measurement range representative of afirst type of incident light, a second measurement range representativeof a second type of incident light, and a third measurement rangerepresentative of a third type of incident light.
 31. The method ofclaim 30, wherein the first, second, and third type of incident lightinclude at least one of fluorescent light, incandescent light, and sunlight.
 32. The method of claim 28, wherein the first and second wellsinclude at least one of n-type wells in a p-type substrate, p-type wellsin an n-type substrate, shallow diffusions, deep diffusions,combinations of shallow and deep diffusions, source/drain diffusions,and charge gate MOS diode structures.
 33. The method of claim 28,further wherein the first and second wells include wells ofsubstantially similar dimensions.
 34. The method of claim 28, whereinthe indication of spectral content includes a wavelength.
 35. The methodof claim 28, further comprising calibrating at least one of the firstand second photocurrents.
 36. The method of claim 28, furthercomprising: disposing at least one transparent dielectric layer above atleast the first well; and disposing at least one opaque layer above thesecond well.
 37. The method of claim 36, wherein the at least one opaquelayer includes a conductive layer.
 38. The method of claim 28, furthercomprising: generating at least one additional photocurrent as afunction of the incident light at an at least one additional well in thesubstrate, proximate the first and second wells, the at least oneadditional well configured to be shielded from the incident light,respectively; and wherein determining the indication of spectral contentincludes determining the indication of spectral content of the incidentlight, further in response to the at least one additional photocurrent.39. The method of claim 38, wherein determining the indication ofspectral content includes determining a ratio of the first and secondphotocurrents, the ratio providing a measure of spectral content,further including determining at least one additional ratio of thesecond and at least one additional photocurrents, wherein the at leastone additional ratio provides an additional measure of spectral contentof the incident light.
 40. The method of claim 39, wherein the ratio andat least one additional ratio further include at least one of a firstmeasurement range representative of a first type of incident light, asecond measurement range representative of a second type of incidentlight, and a third measurement range representative of a third type ofincident light, respectively.
 41. The method of claim 40, wherein thefirst, second, and third type of incident light include at least one offluorescent light, incandescent light, and sun light.
 42. The method ofclaim 38, further wherein said first, second, and at least oneadditional wells include wells of substantially similar dimensions. 43.The method of claim 28, further comprising: providing at least oneanalog-to-digital (A/D) converter with the first and second wells toform a monolithic integrated circuit, the first and second wells beingcoupled to at least one input of the at least one A/D converter forconverting a respective one of the first and second photocurrent into adigital output.
 44. The method of claim 43, further comprising:selectively multiplexing the first and second photocurrents of the firstand second wells, respectively, to an input of the A/D converter. 45.The method of claim 43, wherein the at least one A/D converterintegrates a respective one of the first and second photocurrents over asufficient time period to average a ripple in the incident light causedby alternating current (AC) lighting.
 46. The method of claim 43,further comprising: establishing a spectral content response based on anoutput of the at least one A/D converter, the spectral content responseconfigured to simulate that which would be observed by a human eye. 47.The method of claim 43, wherein the at least one A/D converter utilizesa logarithmic compression for extending a dynamic range of aphotocurrent received at the at least one input of said at least one A/Dconverter.
 48. The method of claim 28, further comprising: controlling adevice parameter in response to the indication of spectral content ofthe incident light.
 49. The method of claim 48, wherein the deviceparameter includes at least one of a backlight control parameter of adisplay and a color control parameter of a color display.
 50. The methodof claim 49, wherein the backlight control parameter includes at least afirst artificial illumination level for a first type of incident lightand a second artificial illumination level for a second type of incidentlight.
 51. The method of claim 28, wherein the first well includes aplurality of first wells, the plurality of first wells for generating aplurality of first photo currents as a function of the incident light,wherein the second well includes a plurality of second wells, theplurality of second wells for generating a plurality of second photocurrents as a function of the incident light, and wherein the indicationof spectral content of the incident light is determined in response tothe plurality of first photo currents and the plurality of second photocurrents.
 52. The detector of claim 51, wherein the plurality of firstwells further includes an array of first wells and the plurality ofsecond wells further includes an array of second wells proximaterespective ones of the array of first wells.
 53. The detector of claim52, still further wherein the array of first wells and the array ofsecond wells include repetitive arrays.
 54. The detector of claim 52,wherein the arrays of first and second wells form a concentric geometryof first and second wells.
 55. A display controller comprising: amonolithic optical detector including first and second wells in asubstrate, the second well proximate the first well, the first wellconfigured to be exposed to incident light and for generating a firstphotocurrent as a function of the incident light, the second wellconfigured to be shielded from the incident light and for generating asecond photocurrent as a function of the incident light, said monolithicoptical detector further including means, responsive to the first andsecond photocurrents, for determining an indication of spectral contentof the incident light; and a backlight controller responsive to theindication of spectral content of the incident light for controlling abacklighting of a display.